At the very least he faces a long, long road to get another opportunity to race in one of NASCAR's top series.

And that's a shame.

Allmendinger seems like a nice guy, has flashed a bit of potential on the track — despite a highly disappointing 2012 season — and has endeared himself to fans and sponsors with an outgoing, colorful personality.

Allmendinger failed a drug test, tested positive for a banned substance and violated NASCAR's substance abuse policy. No matter how you word it, that's a serious offense, and NASCAR took the appropriate action.

That's too bad for Allmendinger, who insists he didn't knowingly take a banned substance and swears he doesn't know what triggered the positive result. Through his agent, he admitted that it was a stimulant — though he has declined to specify what kind — and hinted strongly that it likely came from some sort of supplement he took as part of his physical fitness routine.

He failed his test, his agent says, by nanograms.

Whatever the circumstances, it doesn't matter. Regardless of the source and regardless of whether it was a minor supplement or a serious drug, Allmendinger failed a drug test and must pay the price.

NASCAR came down hard on him and did what it had to do. Its stance is clear — zero tolerance, no excuses.

NASCAR's No. 1 responsibility is to protect the safety of its drivers and fans and the integrity of the sport. It has one of the toughest substance abuse and drug testing policies in sports, and for good reason.

Auto racing is one of the most dangerous games being played. A mistake in racing doesn't just lead to setbacks on the playing field or nagging injuries. It could lead to a violent crash, serious, debilitating injuries, or even death. And it's not just other drivers that are in danger and assume a risk — it's also competitors on pit road, NASCAR and sponsor officials, media, fans and any one else who happens to be near the racing surface during an event.

Any drug or dietary supplement that might impair a driver's ability to perform and to prevent such accidents should be banned and cannot be tolerated. Any drug that might impair a driver's focus, vision, reaction time or mental capacity must be banned.

NASCAR has done that. Now it must back that policy with all its might and come down hard on any driver who violates it, which it did in the case of Jeremy Mayfield and now Allmendinger, the only Sprint Cup drivers suspended since NASCAR implemented random drug testing.

NASCAR has consistently demonstrated that it will not tolerate drug use and has dealt harshly with drivers and crewmen who fail its drug tests. Some have completed the sport's Road to Recovery program and returned to competition. Others have not.

And in the most controversial and high-profile case, Mayfield was suspended for allegedly testing positive for methamphetamines. Mayfield denied that and fought vigorously against NASCAR and its drug-testing program. He has since been charged with possession of meth, however, and has dropped his case against NASCAR as his life continues to unravel.

We don't know what Allmendinger tested positive for, and likely never will, which is unfortunate for Allmendinger because it leads to all sorts of rumors and speculation.

Many fans will give Allmendinger the benefit of the doubt and sympathize with him. Many will paint him as a victim and NASCAR as the evil empire that went too far and ruined another driver's career.

Try telling that to the other 42 drivers on the track who must now wonder what Allmendinger was taking while they raced against him. Or whether others might be guilty, too, and just haven't been caught yet.

Unless Allmendinger reveals what he tested positive for and produces evidence that shows why it produced a positive drug test, we likely will never know the drug in question. NASCAR refuses to divulge it — and under its policy, it has that right — so the burden of proof is on Allmendinger.

Maybe he is a victim of circumstance. Maybe he did take a harmless stimulant or supplement he thought was OK. Maybe he innocently took something that he didn't know contained a banned substance.

For his sake, let's hope that's the case.

But again, it doesn't matter.

As Allmendinger and other drivers have learned, it's up to them to refrain from taking any substance that might be in question and to closely monitor everything that goes into their bodies.

Clint Bowyer says he doesn't take anything short of aspirin. Jimmie Johnson says he diligently checks every dietary supplement he even considers taking. Every driver must follow suit, and NASCAR has programs in place to help them with that.

Allmendinger might prove to be innocent, the victim of poor judgment or just a horrible mistake. He might recover from all this and get his career back on track. Here's hoping he does.

But NASCAR can't get bogged down worrying about whether the failed drug test was triggered by a simple mistake or a mixture of harmless supplements.

It must deal with cold, hard facts. And the facts are that Allmendinger failed a drug test. Plain and simple.

When it comes to the safety of competitors and the integrity of the sport, extenuating circumstances shouldn't matter.